1. Field of the Invention This invention makes modifications to the electronic circuitry of crystal controlled watches and clocks. The modifications permit regulation of the timekeeping rate crystal controlled watches and clocks.
2. Description of the Prior Art
In about 1960, crystal controlled watches and clocks introduced a major improvement in the timekeeping accuracy of wrist watches, desk clocks, floor clocks, clocks installed in process control devices, etc.
A crystal controlled watch or clock typically utilizes a quartz crystal that is intended to vibrate at a frequency of exactly 32,768 hertz (32,768 vibrations per second). The crystal vibrations are electrically driven, usually by battery power.
An electronic counter in the watch or clock counts each vibration of the crystal. When the counter totals 32,768 vibrations, the time display is advanced one second.
It is virtually impossible to manufacture a crystal so that the crystal will vibrate at exactly 32,768 hertz. If the crystal vibrates at 32,768.2 hertz (instead of the desired 32,768 hertz) the watch or clock will gain time at a rate of 16 seconds per month. (0.2 vibrations per second .times.3,600 seconds per hour .times.732 hours per month (divided by) 32,768 vibrations per second=16 seconds per month.) A shock to the crystal, such as dropping a watch, may change the rate of vibration and thus the timekeeping accuracy. Aging of the crystal may also change the rate of vibration and timekeeping accuracy.
At present, crystal controlled watches and clocks do not include any provision for adjusting an incorrect rate of timekeeping. A quartz watch that gains 16 seconds per month will consistently add 16 seconds each month. After four months the watch will be a little more than one minute fast.